Pattern analysis of brain activity for unique and cardinal hues in human visual cortex.

Abstract

Brain activity in response to color stimuli was measured by fMRI. The colors were either cardinal hues of cone-opponent color space or unique hues. Cardinal hues are defined by physiological properties of cone-opponent cells and are known to be fundamental hues in early stage of visual area. Unique hues are known to be the fundamental hues of color appearance. The response patterns of the visual areas V1/V4 were compared. Correlations of brain activity patterns across trials were significantly higher for unique hues, when compared between runs with letter (two-back) task and color (identification) tasks. The result implies that unique hues are better represented in visual areas when the subjects were paying attention to identification of the stimulus hue.